I haven't heard the other 2 but the Ep350v3 will give that added bass you are missing from the V2 and you would probably only need 1, the v2 is anemic compared to the v3. I have heard an ST3 and it was pretty good and for a room of your size would also work great, but the v3 I think is a smoother sounding sub.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70